In his first-ever interview, the sole Australian survivor of the Waco siege has revealed to 60 Minutes what really took place during the 51-day stand-off, and why he believes crazed cult leader David Koresh will one day return to Earth as the son of God.

Dual-citizenship the ultimate disrupter

It was an explosive end to a week that has seen federal parliament hit by revelations of dual-citizenship.

Crossbench senator Nick Xenophon confirmed on Saturday he was a British overseas citizen by descent as a result of his father emigrating to Australia from a British territory.

"I never contemplated that I could have been a British colonial citizen, and that is why I didn't go through an act of renunciation with the UK," he told reporters in Adelaide.

The NXT senator is the seventh federal politician to fall foul of Section 44 of the constitution, which bans dual nationals.

"It is such an unusual and rare position," Senator Xenophon said.

The senator will refer himself to the High Court, sitting as the Court of Disputed Returns, when parliament resumes in two weeks time and says he will continue to vote in the Senate.

"Overnight and this morning I have sought legal advice from a leading constitutional lawyer, and it is appropriate that I keep working hard for South Australians in the Senate until the case is determined later this year," he said.

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The parliament has already referred senators Matt Canavan, Larissa Waters, Scott Ludlam and Malcolm Roberts, as well as Deputy Prime Minister Barnaby Joyce to the court.

On Friday, Deputy Nationals Leader Fiona Nash revealed she was a UK citizen by descent - the third member of Malcolm Turnbull's cabinet to be affected.

This puts the government's majority of one seat in the House of Representatives at risk should there be an adverse ruling by the High Court, with a decision expected in December.

Of the entire crossbench in the lower house, only Indi MP Cathy McGowan has guaranteed to support government bills ahead of the High Court's consideration of referred cases.

"My primary concern is to support good governance," Ms McGowan said on Saturday.

"This is the basis on which I committed to supporting the government on supply and confidence."

The member for Indi joined other crossbench politicians in the upper and lower houses to call for a full audit of the citizenship status of those in the 45th parliament.

"This proposal may be seen as 'too little, too late', but it would be a positive step towards increasing transparency and compelling all members to reveal their citizenship status," she said.

Speaking to reporters in Melbourne on Saturday, Greens leader Richard Di Natale said it was time Malcolm Turnbull showed leadership and supported the audit.

"We've got the support of every member of the crossbench and yet we've got a Coles and Woolies of politics getting together trying to do everything they can to protect their own patch," Senator Di Natale said.

On Twitter, conservative crossbench senator Cory Bernardi reacted to Senator Xenophon's announcement by repeating his calls for parliament to be prorogued.